System.Exception: Error executing 'CREATE_MAILBOX' task on 'User Name' EXCHANGE ---> System.Web.Services.Protocols.SoapException: Server was unable to process request. ---> Connecting to remote server mailbox.cloudmotion.ca failed with the following error message : The WinRM client received an HTTP bad request status (400), but the remote service did not include any other information about the cause of the failure

It should communicate over https yes (and no additional changes for Exchange is needed for that other then the auth method).

Can you verify your using the local powershell url for solidcp? ( https://myserver1.mydomain.local/Powershell )

This issue was fixed with paid SolidCP support, which I would recommend. The issue turned out to be a missing https bind for ip 127.0.0.1 on the default web directory.

I had the same issue after updating to CU23 and Hafnium patch after recent vulnerability.

Fix for us was to use ECP and change Virtual Directory setting for Powershell

and as above "It needs “Integrated Auth” checked (and nothing else) on the auth tab."

save and iisreset - all working again..

Just thought it might help someone else!